The Discovery Channel has a video on erosion that may help us out this week! So might this from howstuffworks.com, but their stuff tends to be a little more dry. Disclaimer: I have not watched these videos in advance.
National Geographic has some (of course) striking photos of weathering and erosion, and this site has various sites with animation on erosion.
This site has a ton of erosion activities, mainly for older students, as well as a graphic organizer, power point presentations, quizzes--even crossword puzzles.
For younger kids, here's a Magic School Bus project on erosion, complete with a printable.